1. Field of the Invention
The present invention concerns a method for showing three-dimensionally defined fiducial points in a video camera image, it relating more particularly to a method of visually verifying the correct position of an object and, especially, to a method of visually verifying the correct position of a patient in surgery. The invention concerns furthermore an apparatus for implementing such methods or for visually verifying the correct position of an object.
2. Description of Prior Art
In particular, in the field of medicine for quite some time one has turned to providing systems which optically assist localizing or positioning of patients, of body parts requiring treatment, or of instruments in the operating room with the aid of a computer.
Conventionally, e.g. in radiotherapy, the position of a tumor as displayed in an x-ray image, or images of another imaging method, is marked by tinting the skin of the patient before aiming the radiation beam at this position and then activating radiation.
Since these methods are hampered by being very inaccurate and fail to meet the accuracy with which radiotherapy/surgery is nowadays possible, systems have been developed which provide computer-assisted precise positioning.
For example, patient landmarks are applied to the surgical target site so that the position of the target volume relative to the landmarks can be precisely mapped by means of a CT scan and saved in a data record. Then, when the patient is brought into the radiosurgical unit, the position of the landmarks can be mapped three-dimensionally by a navigation system, comprising, for instance, two infrared cameras connected to a computer, and the position of the lesion targeted in the operating room can be determined with the aid of the data record from the CT scan. As soon as the spatial location of the focal point of the radiosurgical unit is made known to the computer, the target volume can be precisely brought to this focal point with the aid of this data for then implementing exact target radiosurgery.
Precise positioning in this way is, of course, just as applicable in any other technical application requiring the exact location of an object.
Problems exist, however, in this approach due to no verification mechanism whatsoever being available. In other words, for example, once the patient has been positioned as explained above, the radiosurgeon has to place absolute faith in the system when he switches the radiosurgical unit on, since he no longer has any means of making a visual check with adequate precision and is unable to establish whether malpositioning might have taken place, for instance, due to a glitch in the system.
It is thus the object of the present invention to provide a method and apparatus permitting verification of computer-assisted positioning procedures as discussed above.
This object is achieved in accordance with the invention by a method for showing three-dimensionally defined fiducial points in a video camera image including:
monitoring a spatial region by at least two cameras which can map invisible light, especially infrared light, and by at least one video camera;
computer-assisted analysis of the image data of the cameras using the three dimensional data obtained by means of the invisible-light cameras to compute the spatial location of objects located in the monitored spatial region and mapped by the invisible-light cameras; and
outputting on to a display the fiducial points assigned to the objects together with the video image.
The advantage of the method in accordance with the invention is basically that visual verification is now made possible. When objects are brought into the spatial region monitored by the cameras they are mapped, on the one hand, by the video camera and, on the other, by the two other invisible-light cameras, and following analysis and assignment of the data it is visible from the display whether the fiducial points coincide with the video image points of the objects. If this is the case, then it can be safely assumed that the computer-assisted positioning was successful, whereas if there is a discrepancy, the positioning needs to be corrected or repeated.
The special advantage in using invisible-light cameras, i.e. particularly infrared light cameras, is that mapping the position three-dimensionally may be done with no interference from visible light irradiation or reflections and can thus be implemented with enhanced accuracy and less computation.